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03 April 2006

A Year in Texas: Anuran Nights II

Bastrop State Park is probably where the Houston Toad is making its final stand. This may be an unduly pessimistic prognosis but the ongoing season, and the probability that climate change will produce yet more droughts in our region, does not leave much room for optimism. We finally heard our elusive species two nights ago, but not at Stengl where we’re still hoping to work. Mike Forster of Texas Tech University (San Marcos), who’s been surveying the toad for several years now, had heard plenty of calls at Bastrop State Park on the night of the 30th, while we were keeping our unsuccessful vigil at Stengl. They had kept on going until 4.45 a.m.

Forster suggested using Bastrop as a baseline, to find out which nights the toads are out, and then address whatever that’s going on (or not going on) at Stengl. That makes perfect sense. So we decided to monitor both places on the night of the 1st. It wasn’t particularly onerous going back and forth between the sites. Though about ten miles apart, most of the drive is along Park Road 1C, the “scenic route” connecting Bastrop and Bueschler State Parks. It is, indeed, a pleasant route, winding through Lost Pines, through plenty of forest stands still in sterling health. We stopped periodically along the road in the late evening, listening for our favorite toad but only heard the whistling of the wind through the pines. Much of this land is now in private hands but should probably be a prime target for acquisition for conservation organizations. Especially if the Houston Toad matters. At present, we can only imagine a well-managed belt of prime forest north of Highway 71, stretching from Bastrop to Smithville. But with luck, it may happen.

To return to the Houston Toad: at Bastrop State Park, the toad started calling around 7 p.m. near the lake. Only a few calls at first but, eventually, between 6 -10 individuals; most calls were concentrated in the northern half. Many of the calls came from higher ground, but that’s what you’d expect from a toad. We could not spot any of the individuals but were constrained by what we could legally do in a state park with, as yet, no official research permit. (That’s the agenda for next week.) An occasional leopard frog (Rana sphenocephala) call was the only other anuran activity; there was no chorus, at least not before we left, a little after 8.30 p.m. It was a very warm evening, though overcast, and with a wind at about 15 mph. ruffling the relatively placid surface of the lake. The water was surprisingly clear, with plenty of life, including small black and orange striped water snakes that defied immediate identification. But the drought has affected it, like every other body of water around here. The lake is a fraction of what it is in a good wet year.

The contrast at Stengl could hardly be stronger. For Steve Lanier and me, it was a long night, artificially lengthened by getting lost after midnight. There were a few Rana sphenocephala calling at the pond but, unlike two nights ago, no semblance of a genuine chorus. We didn’t find a single specimen along the bank, compared to the scores on the earlier night. The difference in conditions? Well, we arrived later, at 9.30 rather than 7.30, but there had been a moderate chorus at least as late as 10 p.m. on the 30th. It was far more overcast, warmer, more humid, and with a moderate wind. We need to control variables, but that’s a long term job. But I would bet—not much, but a book or two—that the time of evening is critical. (Skeptics will wonder why I make so much fuss about the behavior of our most common frog. The point, though, is that unless we know how to predict these behaviors we probably have no chance with something apparently as finicky, and now so rare, as our endangered Houston Toad.) For once we’d remembered our nets, and surprised a Gray Treefrog (Hyla versicolor), besides several bluegill sunfish (Lepomis macrochirus). The most intriguing find at the pond was a large bufonid, which uncooperatively avoided the net. It was almost certainly Bufo nebulifer, because of the bridge between the eyes.

At the ephemeral ponds along the creek we did what we could with our nets. To monitor them properly will require more of the students to come out—I obviously have not been sufficiently inspiring. (Or threatening?) Rana sphenocephala were plentiful, along with the Green Treefrog (Hyla cinerea) which has become a personal favorite over the years. Both occurred on higher ground besides the ponds themselves. These ephemerals should be prime Houston Toad territory. But there was no hint of their presence. There were a few bufonids, almost certainly Bufo nebulifer, but none waited long enough for confident identification.

Does the Houston Toad still exist at Stengl? I’m getting increasingly convinced that we won’t find Rana sphenocephala and Bufo houstonensis together, at least in large numbers. The interesting question will be why. We need to understand its habitat requirements better if the Houston Toad is not to disappear in the wild. But there are many more ephemeral ponds along the creek than what we’ve looked at during the last week. On the 30th, we looked at three on the southern segment. On the 1st we looked at one of these, and four more along the northwestern segment. The northern segment remains unexplored. Stengl may yet turn up a Houston Toad.Meanwhile, as usual, Stengl brought many pleasant non-anuran surprises. Earlier in the day, at the pond two goose-like Black-bellied Whistling-ducks (Dendrocygna autumnalis) enchanted us with their rare beauty: the long graceful neck, bright reddish bill, pink legs. These were at the limit of their northern range; we were lucky to have seen these birds and I’d never seen them this far north before. When disturbed, as the field guide said, they flew straight into the tree stands. After all, they like to nest in hollows in trees, somewhat strange behavior for a duck. And we say our first Monarchs, sipping nectar from a stand of yellow Texas groundsel (Senecio ampullaceus), endemic mainly to eastern Texas. Cattle are supposed to be poisoned by this plant but Monarchs have a decided preference for them, and other toxic plants. I will have more on the Monarchs later—they are among my favorite phenomena in Texas. Altogether, it was a pleasant day, and night—in spite of getting lost as we did at Stengl.